Have you checked over on the lighting forum and did a search for recessed lighting? I know there are tons of people who post their floor plans and get help on this. There are some lighting experts over there that can tell you about lumens and foot candles and all that technical stuff. Of course there may be someone here who can do that also, I don't know for sure.

Most lighting stores (if that's who you're buying from) do a layout for free.

I'm not sure what the formula is to make sure you have enough lighting per square footage, but I remember finding one online when I was looking for a chandelier.

Just make sure you have more than enough. You can use dimmers so you have more control over the lighting so it's not always lit up. My kitchen area recessed lighting is extremely inadequate so we're taking advantage of redoing the drywall throughout the house by putting in more recessed lighting.

For a room about 18 X 19 overall but not square, I have 5" recessed lights about 4' apart. When we added them, I put them on 4 separate lines so that you can put on only those you want. All our ceiling lights, except the fluorescent in the laundry, are on dimmers. There's only one over my sink, which gets turned on the most because is provides a nice nightlight, six over the cooktop island which I seldom turn on, perpendicular runs in the entry area and along the oven/micro/refrigerator bank. Instead of a recessed over our breakfast niche, we installed a chandelier, but in our previous homes we've preferred a recessed there also because of the exterior views.

Be sure to get the remodeling type cans and not the ones for new construction.